Lec 11 Life in the Solar System

Associated with carbonate globules carbonate globules

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Unformatted text preview: 994  AH84001 joined the Mars club! ! History: formed from magma ~ 4.5 × 109 yr ago ! Fractured by meteorite impact! Carbonate globules, … !in cracks ~ 3.6 × 109 yr ago ! Blasted off Mars by impact ! 17 × 106 yr ago ! Fell to Earth ! ! ! 13 × 103 yr ago! ! So, known to be from Mars before issue of life arose! Signs of Life?! McKay et al., Science, 273, 924 !(Aug. 16, 1996)! ! Found in fractures - ~ 3.6 × 109 yrs old! When water existed! ! 1.  PAHs - can be produced by breakdown of ! !biological tissues! !Contamination from Antarctic Ice?! !Different mixture of PAHs! !Not necessarily biological - also found in space,! !interplanetary dust, other meteorites, …! !Associated with carbonate globules! Carbonate globules! Evidence of liquid water formation temperature is disputed! 2. Carbonate Globules (50 µm across)
 ! ! ! ! ! !! ! cores of ! manganese! & rings of iron carbonate! ! and iron sulfide! ! similar to globules associated with bacterial! ! action in liquid on Earth! ! !Can form without bacteria on Earth! !! !Dispute about temperature at which globules formed ! ! 3. Magnetite Grains!100 nanometers (nm)
 ! ! !(100 × 10-9 m = 0.1 µm) 
 !! ! ! ! ! ! ! !! Shapes similar to !crystals produced by bacteria on Earth! Other shapes seen by other workers! Whisker shapes suggest formation in hot fumaroles! 4.  ! Fossilized Bacteria?! !!With scanning electron microscope, see ! !!bacteria-like shapes (20 - 100 nm long) similar to those seen in Earth rocks near hot springs !! (R. Folk - UT Austin) described as nanobacteria ! !! ~ 10 - 100 × smaller than normal bacteria! Are these artifacts of process used by microscope (gold coating)?! Need to section and look for membrane - very difficult! Martians??! Later Developments! 1.  Several studies support lower temperature! !for carbonate globule formation - consistent with! !life! ! 2.  Folk finds similar shapes in Allende meteroite ! !(not from Mars)! 2011: Claim of cyanobacteria-like fossil organisms in several carbon-rich meteorites.! 4.  Bada et al., 1998, Science 279, 362 Found amino acids, suggestive of terrestrial contamination! 5.  Many more meteorites from Mars being found.! !! Venus Express Orbiter! •  Venus Express Orbiter, an ESA mission! –  Launched Nov. 2005, arrived Apr. 2006! –  Studying atmosphere, surface with radar! –  Learning about methods of water loss! –  http://www.esa.int/SPECIALS/ Venus_Express/SEMOD3808BE_0.html!...
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This note was uploaded on 04/05/2013 for the course UGS 302 taught by Professor Staff during the Spring '08 term at University of Texas.

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